Temperature-compensated springs



June 26, 1962 R. STRAUMANN 7 3,041,163

TEMPERATURE-COMPENSATED SPRINGS Filed Aug. 51, 1959 G FIE. l

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3,041,163 Patented June 26, 1962 3,041,163 TEMPERATUREQQMPENSATED SPRWGS Reinhard Straumann, Waldenburg, Basel-Campagne,

Switzerland, assignor to lnstitut Dr. Ing. Reinhard Stranrnann A.G., Waldenhurg, Switzerland, a body corporate of Switzerland Filed Aug. 31, 1959, 'Ser. No. 837,037 Claims priority, application witzeriand fiept. 4, H58 9 Claims. (Cl. 75-423) This invention relates to temperature-compensated springs, primarily for clocks, watches and precision mechanisms, and has for an object to provide a material for such springs whose thermoelastic coeflicient is constant, or substantially constant, over the working range of temperatures.

When the modulus of elasticity-which normally varies with temperatureof a spring is wholly or substantially independent of temperature over a certain range, the spring is said to be temperature-compensated over that range. This'is desirable both for static springs, as used in precision spring balances, and for oscillatory springs, as used in precision clocks and watches.

Alloys for use in the manufacture of temperature compensated springs are already known, and are described, for example, in Swiss patent specifications Nos. 160,798, 166,535 and 196,408, which disclose hardenable Ni-Fe alloys with additions of beryllium. However, even these alloys exhibit variations in the thermoelastie coefiicient which are unacceptable for certain purposes, as will be more fully described hereinafter with reference to the accompanying drawings which show the performances of various springs in terms of timekeeping at various temperatures. In the drawings:

FIGURE 1 is the timekeeping/temperature curve for a spring of one of the said known alloys;

, FIGURE 2 isa similar curve for a first spring accord ing to the present invention, and

FIGURE 3 is a similar curve for a second spring 210-. cording to the present invention.

The thermoelastic coefficient, is defined by the equation where:

T and T are chosen values of operating temperature which, for clocks, are usually +4 Cpand +36 C., respectively FIGURE 1 shows the timekeeping characteristic G of a clock with a spiral spring of one of the said known alloys as measured over a range of temperatures, 'At +4 C. this clock runs 7 seconds per day slow; at 20 C. it runs 4 seconds per day fast; and at 36 C. it runs 3 seconds per day slow. The mean thermoelastic ooefiicient thus amounts to only 1.4 l per degree centigrade, whereas the thermoelastic coefiicient of steel is about 200 l0 per degree Centigrade. However, the secondary error f the devia ion of the timekeepin c ract n' io G at he inte med a e tempe a re, 2 fr he v lue wh ch it would have if the t mek ep ng ven' lin ly w n C. and +36 Q-amounts to 1 seconds p r day. S ch a piral pring has therto e n considered good in clock manufacture, though a spring with a smaller secondary error or, if possible, without any secondary error has always been desired.

It is an object of the present invention to provide an alloy from which springs may be produced not only with small positive or negative mean thermoelastic coeflicients, but also having a substantially smaller secondary error than those hitherto known. For example, the secondary error of a spring according to the present invention should be at most, 5 seconds per day, and preferably not more than 3 seconds per day, in the temperature range of +4 C. to +32 C. I

The modulus of elasticity of one known alloy has a value at +32 C. which is only .01 percent higher than at +4 C. whilst at 20 C. it is .03 percent higher than at +4 C. For springs for sensitive spring balances or precision instruments, however, deviations at 20 C. of not more than .015 percent and preferably not more than .01 percent are desirable.

Obviously thematerial for such a spring, if it is to answer all requirements, must be hardenable, must have low inherent damping, and must in particular be substantially non-magnetic.

Extensive experiments have now shown that a Ni-Fe-Mo alloy with an addition of beryllium satisfies these requirements, and in accordance with the present invention has the following composition:

, Percent Ni 35-45 Mo 7-12 Be 0.1- 1 Cr u 0- 3 Mn-l-Si 0 3 Fe Remainder Alloys of the following compositions have proved particularly advantageous:

Fe d Remainder EXAMPLE 1 A wire 0.6 mm.

in diameter was prepared from an alloy containing:

This wire was heated to incandescence for 10 minutes at 1150 C., was quenched in water and, without inter-. mediate reheating, was drawn down to a diameter of 0.33 mm. Spiral springs were wound from this material, and these springs were heat-treated for one hour at 500 C. The springs were excited at their natural frequencies and the oscillation frequency was compared with a standard clock controlled by a quartz oscillator. Table 1 and FIGURE 2 of the drawings show the timekeeping of an oscillating system based on this spring in seconds per day as a function of the temperature.

3 :3 Table 1 Temperature,0 30 13 +7 +28 +50 +67 T1mekeeping(sec.lday) 6 1 +1 +1 6 16 It will be seen that such a spring not only has a low secondary error of about 0.5 second per day, in the temperature range of +4 C. to .+32. C., but also has a considerably wider range of temperature compensation than the known alloys.

EXAMPLE II A wire 0.5 mm. in diameter was produced from an alloy containing:

Percent Ni 39 Mo 9 Si 0.4 Fe Remainder This wire was heated to incandescence in a tunnel oven at 1120 C. and quenched in water. By cold-drawing and subsequent cold-rolling a ribbon 0.2 mm. in breadth and 0.02 mm. in thickness was produced. This was wound into spiral springs, and the springs were heated to incandescence for 30 minutes at 650 C.

A Watch equipped with such a spring was observed at various temperatures and its timekeeping is shown in Table 2 and in FIGURE 3.

Table 2 Temperature, 0 70 80 Timekeeping (see/day) +8 +2 +6 +8 This test also shows clearly the superiority of the alloy in accordance with the invention, for which, with a small secondary error, there is also a wider temperature compensation range.

EXAMPLE III A wire of 3 mm. diameter was prepared from an alloy containing:

Percent Ni 40 Mo 9.5 Be 0.4 Mn 0.5 Si 0.3 Cr 2 Fe Remainder Table 3 Temperature C) Deviation of spring constant (percent) This test again shows the improvement afforded by alloys in accordance with the invention. A further advantage of those which contain chromium is that they have less magnetic permeability than the alloys hitherto used for spiral springs, while at the same time the corrosionresistance is improved.

From the foregoing analysis, it will be evident that not only does a nickel-molybdenum-iron alloy having an addition of beryllium permit the manufacture of a spring hav ing a much smaller secondary error 1, but also the range of temperatures over which this secondary error does not exceed that for known alloys is much greater.

I claim:

1. A temperature-compensated spring of a hardenable Ni-Fe-Mo alloy containing beryllium and having a low secondary error in addition to a low thermoelastic coefficient, and spring having the following composition:

Percent Ni 35-45 Mo 7-12 Be .-.a 0.1-1 Cr Up to 3 Mn+Si Up to 3 F Remainder 2. A spring according to claim 1 wherein the alloy has the following composition:

Percent Ni 38-40 Mo 9-10 Be 0.5-0.8 Cr Up to 3 Mn+Si Up to 3 Fe Remainder 3. A spring according to claim 1 wherein the alloy has the following composition:

Percent Ni 39-41 Mo 9-10 Be 0.3-0.5 Mn+Si 0.5-1 Cr 1.5-2.5 Fe Remainder 4. A spring according to claim 2 wherein the alloy has the following composition:

Percent Ni 39-40 Mo 9 Be 0.5-0.6 Mn+Si 1-1.5 Fe Remainder 5. The method of manufacture of a temperature-compensated spring having a low secondary error in addition to a low thermoelastic coeflicient, said method comprising making a wire from an alloy containing Percent Ni 40 Mo 9.0 Be 0.5 M11 0.87

Si 0.21 Fe Remainder and heating said wire for 10 minutes at 1150" C.; quenching same in water, cold-drawing to approximately half its original diameter; forming said wire into a spring of the desired dimensions, and heat-treating for one hour at 6. The method of manufacture of a temperature-compensated spring having a low secondary error in addition to a low thermoelastic coeflicient, said process comprising making a wire of 0.5 mm. diameter from an alloy containing Percent Ni 1 39 Mo 9 Be 0.6 Mn 0.62 Si 0.4 F Remainder and heating to incandescence at 1120 C.; quenching in water; cold-drawing and rolling to a ribbon of 0.2 mm.

breadth and 0.02 mm. thickness; forming a spring of the desired dimensions, and heating to incandescence for 30 minutes at 650 C.

7. The method of manufacture of a temperature-compensated spring having a low secondary error in addition to a low thermoelastic coeflicient, said process comprising making a wire from an alloy containing Percent Ni 40 Mo 9.5 Be 0.4 Mn 0.5 Si 0.3 Cr Fe Remainder heating to incandescence at 1150 C., quenching, and cold-drawing to half its original diameter; forming the desired spring, and heating for one hour at 550 C.

8. A temperature compensated spring having a low secondary error in addition to a low thermoelastic coefiicient, said spring having the following composition:

, I Percent Ni 40 M0 9.0

Percent Mn 0.87 Si 0.21 Fe Remainder 9. A temperature-compensated spring having a low secondary error in addition to a low thermoelastic coeificient, said spring having the following composition: 

1. A TEMPERATURE-COMPENSATED SPRING OF A HARDENABLE NI-FE-MO ALLOY CONTAINING BERYLLIUM AND HAVING A LOW SECONDARY ERROR IN ADDITION TO A LOW THERMOELASTIC COEFFICIENT, AND SPRING HAVING THE FOLLOWING COMPOSITION: 